The subject matter disclosed herein relates generally to image detectors, and more particularly to pixelated solid state image detectors and photon detection with the detectors.
Detectors for diagnostic imaging systems, for example, detectors for single photon emission computed tomography (SPECT) and computed tomography (CT) imaging systems are often produced from semiconductor materials, such as Cadmium Zinc Telluride (CdZnTe), often referred to as CZT, Cadmium Telluride (CdTe) and Silicon (Si), among others. These semiconductor detectors typically include arrays of pixelated detector modules. The spatial resolution of pixelated solid state gamma ray detectors is limited by the size of the detector pixels. The minimal pixel size is also limited by the solid state physics and engineering.
During the interaction of gamma ray in a CZT detector, a charge cloud is developed between the continuous cathode and the pixelated anode. This cloud grows moving toward the anode side of the detectors. In conventional systems, each pixel anode is connected to a preamplifier and a large number of readout channels per pixel (e.g., 256 readout channels). Thus, as pixel size decreases to improve spatial resolution, the number of total readout channels increases, thereby increasing the complexity of the electronics, controllers, cost and heat production. Accordingly, gamma and x-ray detectors using direct conversion semiconductor materials such as CZT or CdTe are manufactured with relatively large pixel sizes to reduce complexity of the electronics (e.g., reduce application specific integrated circuit (ASIC) complexity) and reduce or avoid charge cloud sharing between adjacent pixels.
However, this large pixel size does not perform satisfactorily for x-ray and CT applications. Additionally, in SPECT systems, image performance is directly related to the number of detector pixels.